BuddyPress.org

Hi guys, can someone explain me what’s the difference between following a member and having him as friend ?
What’s the purpose of each functionnality ?

Btw; i’m working on a classified ads component and i would like to have a functionnality to automatically warn members when particular users posted new ads.

The idea is to have the ability of “following” an ad author; but I don’t understand if I have to add a specific “follow” function for my plugin or if I could integrate that (and if this is a good idea) with the core system.

Any suggestion ?